Dry glass reference perturbation theory predictions of the pervaporation separation of solvent mixtures using PIM-1 membranes

Abstract

In this paper a new model to predict the pervaporation separation of solvent mixtures with glassy polymer membranes is proposed. The diffusion theory is that of Maxwell-Stefan diffusion with a concentration gradient driving. The specific form of the diffusion theory allows for the solution of systems of algebraic equations, as opposed to differential equations when chemical potential gradient driving forces are used. The bulk phase behavior is modelled using the perturbed-chain statistical associating fluid theory (PC-SAFT). The guest species solubilities in the membrane at the retentate and permeate boundaries are evaluated with the dry glass reference perturbation theory (DGRPT) closure of the non-equilibrium thermodynamics of glassy polymers (NETGP). The approach is applied to the pervaporation of solvent mixtures with PIM-1 glassy polymer membranes. It is demonstrated that the model can accurately predict the pervaporation of binary solvent mixtures, using only pure vapor solubility data to parameterize DGRPT, and pure component diffusivities measured from pure vapor diffusion in PIM-1 films. This predictability and comparatively simple form of the theory will allow for the implementation in process simulators to allow for the screening of membrane-based processes based on a minimum of data.